First and foremost, this started appearing on the BETA of Mac OS ( 10.13) , so I'm well aware of the implications of running BETA software. I'm just trying to understand where/what may be going on, as I see most CL failures from old Linux threads dealing with old GPUs and old OpenCL issues.

The Project Scientist was made aware of the situation with the Beta OS the day you first posted. I made recommendations for the Project to switch to App versions that didn't have that problem, I haven't seen a response. I'm not surprised the SoG ATI version stopped working, I never could get the nVidia SoG version to work at all, and the ATI version had very bad idle wake up numbers. There are existing Apps that don't have that problem, one is at Beta here, v8.19 (opencl_ati5_mac) App https://setiweb.ssl.berkeley.edu/beta/results.php?hostid=82822, and a newer version is being run on this machine, System: Darwin x86_64 Kernel: 17.0.0
OpenCL version by Raistmer, r3610
Since it doesn't appear any changes are going to be made to the SETI Server, I'd suggest you do what the other Mac user did and switch to Anonymous platform using the r3610 version of the App. It seems your machine also has an AVX2 capable CPU, it should work well with the AVX2 App that's included in the bundle. Normally I'd suggest setting the Manager to No New Tasks and running down the cache before making the change to Anonymous platform, but I guess it really doesn't matter. Follow the instructions and place the New files in your setiathome.berkeley.edu folder, that should stop the Errors.
You want this package, ATi5r3610&CPU-AVX2.7z
Hope that helps.

I still don't see any new tasks in your cache, https://setiathome.berkeley.edu/results.php?hostid=8248108 The new tasks will appear as SETI@home v8 Anonymous platform. It would be best if you either let your existing tasks error out, or abort them before you start running with the new Apps. Otherwise they will be in limbo until they Time-Out late next month. If you haven't added the new Apps yet just set No New Tasks in the Projects tab and let them error out. Once you Add the new Apps change it back to Allow new tasks, the new tasks downloaded will be listed as SETI@home v8 Anonymous platform. I would suggest setting the Preferences for your CPUs to 50% to help cut down heat. The CPU will use the Boost when set at 50% so the tasks will finish a little faster than normal and produce less heat. It's under Options/Computing Preferences/Use at most 50% of the CPUs. Leave the % of CPU time set at 100%. You'd be surprised how fast that CPU will finish a task with the AVX2 App using those settings.

This appears to be a problem with one of the science applications. The BOINC developer for the Mac has sent information to the project developers about this and hopes that they'll build new versions soon, or at least retract the one application causing all the trouble. The rest of the ATI applications doesn't seem to have the problem, only the opencl_ati5_SoG_mac application.Jord

Ancient Astronaut Theorists can tell you that I do not help with tech questions via private message. Please use the forums for that.

The Sister App to 8.20 SoG was launched at Beta at the Same time. The only difference is it doesn't use the SoG path and is numbered 8.19, also, it Works with Darwin 17.02.0.https://setiweb.ssl.berkeley.edu/beta/results.php?hostid=82822
It's been in Beta Testing since 8 Nov 2016 and could be swapped with 8.20 in minutes. Why it hasn't been done is anyone's guess.
The Newer App ATi5r3610 is just a newer version of ATi5r3552 and was recommended to Beta long ago. Both of these Apps work in MacOS 10.13 - High Sierra and have been available for a Long time.

The Sister App to 8.20 SoG was launched at Beta at the Same time. The only difference is it doesn't use the SoG path and is numbered 8.19, also, it Works with Darwin 17.02.0.https://setiweb.ssl.berkeley.edu/beta/results.php?hostid=82822
It's been in Beta Testing since 8 Nov 2016 and could be swapped with 8.20 in minutes. Why it hasn't been done is anyone's guess.
The Newer App ATi5r3610 is just a newer version of ATi5r3552 and was recommended to Beta long ago. Both of these Apps work in MacOS 10.13 - High Sierra and have been available for a Long time.

What do you consider safe? The 8.19 App was compiled on the Exact same Computer as most of the other Mac Apps, including 8.20, and is currently on the Berkeley server. All you have to do is Join SETI Beta and it will be downloaded to your Host automatically, just as the other Macs at Beta. Then all you have to do is move it to the SETI Main folder and work up an Anonymous platform package. Or you could just use the package that has already been configured at Crunchers Anonymous with the newer r3610 App that was compiled on the same computer. If you want to configure the 8.19 App at Beta for use at Main you can download the Files from here,http://boinc2.ssl.berkeley.edu/beta/download/setiathome_8.19_x86_64-apple-darwin__opencl_ati5_machttp://boinc2.ssl.berkeley.edu/beta/download/MultiBeam_Kernels_r3552.cl
I would suggest you use the r3610 package as a guide if you are determined to use the older 8.19r3552 App.
Personally, I'd go with the r3610 package, it's a little faster on the BLC tasks.